Skip to content



It is known that a common practice is to place the radiators are the finest for different motifs, I felt the most normal the assume that only the finestres are not mobile, but there is a justification of the technical reason why it is based on the finestres i és, Exactly what we were going to report on in this article.

To a system heating installation of water radiators (boiler and heating water pipes) is done due forms of heat dissipation that are:

1.- Per radiació (hence the name of radiators): emit heat through the entire surface in a radial way, but I felt the “force” enough for the comfort temperature to reach the as quickly as possible to the environment.

2.- Per convection: it generates a current d’aire that is the one that heats the air, but that it is not “mou” with the force enough for the comfort temperature to arrive as quickly as possible l’ambient.

When the temperature difference is greater between a radiant cos and its surroundings, the greater the quantity of energy radiated by a mateixa temperature of the radiant cos that is that of the water that crosses the radiators.

The heat is released by convection depending on the air velocity to the lower part of the radiator and the height of the elements of the radiator. The more height, the more difference in atmospheric pressure and the more recirculation existix. (fixeu-vos that, malgrat that sembli that pressed her atmospheric pressure cannot vary due to the height of the radiator, when it is high atmospheric pressure -bon temps- the water from the siphon of the toilet is lower. Aixo shows that atmospheric pressure is also notable at these levels).


Ara vaig to pose an analytical example  to calculate the yield loss energètic that supposes the separation of the radiators from the finestres.

The best are envidrades and donate to the outside; the temperature of the surface of the finestres tea is about 2-4º C Menys that the walls that separate l’habitatge from l’exterior.

For the numerical example we have some conditions Of temperature:

  • Temperature outside 0ºC
  • Temperature of the radiator 50ºC which is the maximum to avoid cremades by direct contact

Both these data and the ones that are obtained from them thermal resistance tables of each element that makes up the facade, The following parameters are obtained:

Superficial thermal resistances :

  • glass double (1/h) = 0.112 mºC/W
  • walls (1/h) = 0.095 mºC/W

Thermal transmission coefficients :

  • glass double (K) = 2.0 W/mºC
  • walls air chamber (K) = 1.2 W/mºC

Applying the formulas correspondents obtain the following results:

If the radiator is Situa sota de la finestra or molt a prop d’ella obtindrem:

  • Energy heat per radiation 205 W/m2
  • Energy heating per convection 160 W/m2

Or followed the radiator cedeix a quantitat of energy equal to the sum of the dues, calorific and per convecció, both a total of 365 W/m2.

Yes, per altra banda, put the radiator on, for example, about 5 m from the finestra to the mitgera wall with the view and both Assumed conditions (50ºC at the radiator water and 0ºC temperature atmospheric), the veí will not be at 0ºC but will be at 10ºC in the pitjor dels cases i haurà menys corrent d’air per convecció that sota la finestra.

Applying the corresponding formulas obtained the following results:

If the radiator is located about 5 m from the finestra ia a paret mitgera amb un veí obtindrem:

  • Energy heat per radiation 192 W/m2
  • Energy heating per convection 55 W/m2

Or did the radiator give up a quantity of energy equal to the sum of the dues, calorific and per convecció, both a total of 247 W/m2.

Això ens indicates that the loss of efficiency energy between the location of the radiator allunyat de la finestra, cap a The interior of the floor, in order to place it next to the finestra, is: 365 – 247 = 117 W/m2 which in percentage means a loss of 32%.


  • The Col·location of the radiators sota les finestres is more efficient
  • quan there is a temperature difference between the environment and the radiator and this is creates a current of air on the air fred passes through the radiator i increases the heat given up by convection. How petite was the difference of lower temperatures will be the velocity of the air at the current of the radiator i lower l’energy transferred to l’entorn per convecció.
  • The efficiency energy of the radiators located inside the rooms pot decrease molt (32%) depending on the temperature of the radiation environment.
  • Is to increase the effect of radiation by col·locating reflective plates darrera dels radiators that are col·locats a parets de façana ia parets on a l’altre Cost of having a non-heated space (built-in cabinets, galleries, etc.)
  • S’augmenta the effect of convecció/radiació recircul.lant l’air col·locant microfans on the radiators to favor the speed of propagation of temperature

Leave a Reply

Your email address will not be published. Required fields are marked *